Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DESCRIPTION
OPTICAL, INFORMATION RECORDING MEDIUM,
OPTICAL INFORMATION RECORDING METHOD, AND
OPTICAL INFORMATION RECORDING APPARATUS
TECHNICAL FIELD
The present invention relates to an optical
information recording medium, an optical information
recording method and an optical information recording
apparatus, for optically recording information. In more
detail, the present invention relates to an optical
information recording medium including a first information
recording layer on which information is to be recorded by
laser light and a second information recording layer on
which information is to be recorded by the laser light which
has passed through the first information recording layer;
and a method and an apparatus for the optical information
recording medium.
BACKGROUND ART
Recently, optical discs, optical cards, optical
tapes and the like have been developed as optical
information recording media for allowing information to be
optically recorded. Among these, optical discs have
attracted attention as optical information recording media
for allowing a large capacity of information to be recorded
at high density.
One type of rewritable discs are phase-change
optical discs.. A recording layer used for a phase-change
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optical disc is reversibly changed to either an amorphous
state or a crystalline state, depending on. the conditions
of heating by laser light and the cooling conditions. The
recording layer has different optical constants when in an
amorphous state from when in a crystalline state. Therefore,
in the case of a phase-change disc, one of-the two states
is selectively formed in the recording layer in accordance
with information to be recorded, and the- resultant optical
change (i.e., a change in transmittance or reflectance) 'is
utilized. Thus, information recording and/or reproduction
can be performed. In order to obtain the two states,
information is recorded as follows. {~{
A recording layer of an optical disc is. irradiated
with pulse-type laser light (referred to as a 'recording
pulse') at a. power for raising the temperature of the
recording layer to equal to or higher than the melting point.
As the laser light passes, the melted portion of the
recording layer is rapidly cooled into a recording mark in
an amorphous state. Alternatively, the recording layer is
irradiated with focused laser light at a power, for raising
the temperature of the recording layer to a point equal to
or higher than the crystallization point but equal to or
lower than the melting point. Then, the portion of the
recording layer irradiated with the laser light is placed
into a crystalline state.
An optical disc is a 'recording medium which is
exchangeably mounted with other optical discs on an optical
' disc recording and reproduction apparatus. Therefore, the
optical disc recording. and reproduction apparatus needs to
stably perform recording on or reproduction from a
plurality of optical discs. Even optical discs produced
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under the same conditions may have different recording mark
states or. maybe differently influenced by thermal
interference between recording marks, due to different
thermal characteristics thereof which are caused by
dispersions at the time of production and/or time-wise
changes. This may result in different recording conditions
including the recording power for the optical disc and the
optimum edge position of the recording pulse.
In order to stably record information without being
influenced by changes in such recording conditions, an
optical disc recording and reproduction apparatus obtains
recording conditions before recording information on an
optical disc. Specifically, before recording information
on an optical disc, an optical recording and reproduction
apparatus performs teat recording using a specific data
pattern (referred to as "test information") , reproduces the
test information, and measures the reproduced signal so as
to obtain the recording condition. This process is referred
to as "test recording". Optical discs have an area used
by the test recording, which is referred to as an "test
recording area".
A rewritable disc has a reproduction-only area
pre-formed in a specific portion. The reproduction-only
area includes convex and concave phase pits. In the
reproduction-only area, information which does not need to
be rewritten, for example, information on the optical disc
itself or address information, is recorded. This area is
also referred to as an "emboss area".
An area in which information is recorded by forming
a recording mark is referred to as a "recording and
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reproduction area". In the recording and reproduction area,
information which ha0 a possibility of being rewritten- Is
recorded.
A general rewritable optical disc has a data area.
in a central. portion in a radial direction thereof, and haw
a lead-in' area in a portion internal with respect to the'
data area, and a lead-out area in a. portion external with
respect to the data area. in general, an area for recording'
management information-of the optical dine and/or o text
recording area is provided in the lead-in area and- the
lead-out area.
Recently, there has been strong demand for the
optical discs with a higher recording density. In response
to this demand, a multi-layer recording medium having two
or more information recording layers in a thickness
direction of the disc is proposed. Information caA, be
recorded on each of-the information- recording layers.
.
In such a multi-layer recording medium, each of the
information recording layers often have different
recording characteristics. This requires test recording
to be performed for each information recording layer. one
exemplary method of such. test recording is disclosed in
Japanese Publication No. 11003550, published 06/01/99.
However,, conventional methods do not consider the
following phenomenon. When test.recording is performed on
an information recording layer of a. multi-layer recording
medium which is far from the laser incidence surface (the
information recording layer far from the laser incidence
surface will be referred to as a "second information
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recording layer ), the second information recording layer
is influenced by the state of an information recording layer
which is closer to the laser incidence surface (the
information recording layer closer to the laser incidence
5 surface will be referred to as a "first information
recording layer").
Laser light 'used for recording information on the
second information recording. layer may become none-uniform
when the laser light has passed through a certain area of
the first information recording layer. In this case, test
recording would not provide accurate recording conditions.
The light transmittance of an information recording
layer varies depending on whether information is recorded
or not in the recording and reproduction area of the
information recording- layer. Therefore, the amount of.
laser light reaching the second information recording layer
varies in accordance with the ratio of an unrecorded area
and a recorded area in a light spot of the laser light on
the first information recording layer, the light spot being
formed before the laser light is used for test recording
on the second information recording layer. As a result,
accurate recording- conditions are not obtained.
The light transmittance of an unrecorded area in the
recording and reproduction area can be considered to be
equal to the light transmittance of the reproduction-only
area. However, the light transmittance of a recorded area
in the recording and reproduction area is different from
the light transmittance of the reproduction-only area.
Accordingly, when test recording is performed on the- second
information recording layer, the amount of laser light
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reaching the second information recording layer varies also-
in accordance with the ratio of the reproduction-only area
and the recording and reproduction area in a light spot on
the first information recording layer (and the ratio of the
recorded area and the unrecorded area in the recording and
reproduction area).
The second Information recording layer is
influenced by the state of the first information recording
layer when information (for example, user data information)
is recorded in'a recording and reproduction area of - the
second information recording layer, as well as at the time
of test recording. In this case also, information cannot
be accurately recorded, which reduces the signal. quality
used for. reproducing the recorded information.
The present invention, to solve these problems of
the prior art, has an objective of accurately obtaining
optimum recording conditions for an optical information
recording medium having two or more information recording
layers, and another objective of accurately recording
information on each of two or more information recording
layers of an optical information recording medium.
DISCLOSURE OF THE INVENTION
An optical information recording medium according
to the present invention includes a first information
recording layer on which information is to be recorded by
laser light; and a second information recording layer on
which information is to be recorded by the laser light which
has passed through the first information recording layer.
The first information recording layer includes at least one
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of a reproduction-Only area and a recording and
reproduction area. The second information recording layer
includes a test recording area. At least -one of the
reproduction-only area and the recording and reproduction
area, and the test recording area is located such that one
of the reproduction-only area and the recording and
reproduction area includes an area of the first information
recording layer through which the laser ).fight for recording
information in the test recording area passes.
The optical information recording medium may
further include a separation layer for separating the first
information recording layer and the second information
recording,layer from each other. The area of the first
information recording layer, through which the laser light
for recording information in the test recording area passes,
may extend outward from an outer end of an .area of the first .
information recording layer corresponding to the, test
recording area by a length 8, the length S being represented
by:
S = d-tan (sin-"(NA/n)')
where d is a distance in a thickness direction between the
first information recording layer and the second
information recording layer; n is a refractive index of the
separation layer: and NA is a numerical aperture of an
objective lens for focusing the laser light to the test
recording area.
The second information recording layer may have a
data recording area which extends from an end of the test
recording area by at least the length S.
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The area of the first information recording layer,
through which the laser light for recording information in
the test recording area passes, may extend outward from the
outer end of the area of the first information recording
layer corresponding to the test recording area by a length
:
the length S' being represented by
$' d=tan (sin",1(NA/n)) + &n
where &n is a maximum positional offset distance between the
first information recording layer and the' second
information recording layer.
The second information recording layer may include
a data recording area which extends from the and of the test
recording area by at least the length $'.
An optical information recording medium according
to the present invention includes a first information
recording layer on which information is to be'recorded by
laser light; and a second information recording-layer--on
.
which information is to be recorded by the laser light which
has passed through the first information recording layer.
The first information recording layer includes a prescribed.
area. The second information recording layer includes a
test recording area. The prescribed area and the test
recording area are located such that the prescribed area
includes an area of the first information recording layer
through which the laser light for recording information in
the test recording area passes. The prescribed area is
entirely in a recorded state or entirely in an unrecorded
state.
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The prescribed area, when being in an unrecorded
state, may be a recording prohibited area.
The prescribed area, when being in an unrecorded
state, may be a mirror area.
The prescribed area, when being in an unrecorded
state, may be a lead-in area.
The optical information recording medium may
further include a separation layer for separating the first
information recording layer and the second information
recording layer from each other. The area of the first'
information recording layer, through which the laser light
for recording information in the test recording area passes,
may extend outward from an outer and of an area of the first
information recording layer corresponding to the test
recording area by a length S, the length 6 being represented
by:
5 = d=tan(sin"1(NA/n)),
where d is a distance in a thickness direction between the
first information recording layer and the second
information recording layer; n is a refractive index of the
separation layer; and NA is a numerical aperture of an
objective lens for focusing the laser light to the test
recording area.
The second information recording layer may have a
data recording area which extends from an end of the test
recording area by at least the length S.
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The area of the first information recording layer,
through which the laser light for recording information in
the test recording area passes, may extend outward from the,
5 outer and of the area of the first information recording
layer corresponding to the test recording area by a length
S', the length S' being represented by:
S' = d=tan(sin'1(NA/n)) + Sm
where ft is a maximum positional offset distance between the
first information recording layer and the second.
information recording,layer.
The second information recording layer may include
a data recording area which extends from the and of the test
recording area by at least the length S'.
An optical information recording medium according
2D to the present invention includes a first information
recording layer on which information is to be recorded by
laser light; and a. second information recording layer on
which information is to be recorded by the laser light which
has passed through the first information recording layer.
The first information recording layer includes a test
recording area and a recording and reproduction area. A
light transmittance of an area of the first information
recording layer,, through which the laser light for
recording information in the test recording area passes,
is different from a light transmittance of an area of the
first information recording layer, through which the laser
light for recording information in the recording and
reproduction area passes. Information for calculating an
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optimum recording condition of at least one of the test
recording area and the recording and reproduction area is
recorded in a, specific area of either the first information
recording layer or the second information recording layer.
An optical information recording medium according
to the present invention includes a first information
recording layer on which information is to be recorded by
laser light; and a second information recording layer on.
which information is to be recorded by the laser light which
has passed through the first information recording layer.
The first information recording layer includes at least one
of a reproduction-only area and a first recording and
reproduction area. The second information recording layer
includes a second recording and reproduction area. At least
one of the reproduction-only area and the first recording
and reproduction area, and the second recording and
reproduction area are located such that one of the
reproduction-only area and the first recording and
reproduction area includes an area of the first information
recording layer through which the laser light for recording
information in the second recording and reproduction area
passes.
The optical information recording medium may
further include a ,separation layer for separating the first
information recording layer and the second information
recording layer from each other. The area of the first
information recording layer, through which the laser light
f or recording information in the second recording and
reproduction area passes, may extend outward from an outer
and of an area of the first information recording. layer
corresponding to the second recording and reproduction area.
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by a length $, the length b being represented by:
$ d=tan(sin-'(NA/n) ),
where d is a distance in a thickness direction between the
first. information recording layer and the second
information recording layer; n is a refractive index of the
separation layer; and NA is a numerical aperture of an
objective lens for focusing the laser light to the second
recording and reproduction area.
The area of the first information recording layer,
through which the laser light for recording information in
the second recording and reproduction area passes, may
extend outward from the outer and of the area of the first
information recording layer corresponding to the second
recording and reproduction area by a length the length
8' being represented by:
S' = d'tan(sin-l(NA/n)) +. &n
where m is a maximum positional off set. distance between the.
first information recording layer and the second
information recording layer.
A size of the reproduction-only area of the first
information recording layer may be-zero.
An optical information recording medium according
to the present invention includes a, first information
recording layer on which information is to be recorded by
laser light;. a second information recording layer on which
information is to be recorded by the laser light which has
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passed through the first information recording layer; and
a separation layer for separating the first information
recording layer and the second information recording layer
from each other. The first information recording layer
includes at a first test recording area and a non-uniform
light prevention area. The second information recording
layer includes a second test recording area. The
non-uniform light prevention area, the first test recording
.area and the, second test recording area are located, such
that a distance between the first test recording area and
the second test recording area is greater than a length 8,
and such that the. non-uniform light prevention area
.includes an area of the first information recording layer
through which the laser light for recording information in
the second test recording area passes, the length 6 being
represented by;
8 m d=tan (sin'1(NA/n)) ,
where d is a distance in a thickness direction between the
first information recording layer and the second
information recording layer; n is a refractive index of the
separation layer; and NA is a numerical, aperture of an
objective lens for focusing the laser light to the second
test recording area.
The first information recording layer may include
at least one of a first. lead-in area and a first lead-out
area. The second information recording layer may include
at least one of a second lead-in area and a second lead-out
area. The first lead-in area and the second lead-in area
respectively may include the first test recording area and
the second test recording area, or the first lead-out area
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and the second lead-out area respectively f.nclude the first
test recording area and the second test recording area.
The non-uniform light prevention area of the first
information recording layer may be a reproduction-only
area.
The non-unif orm light prevention area may be an area .
formed of at least one of the group consisting of a
reproduction-only area, a recording prohibited area, and
a mirror area.
The area of the first information recording layer,
through which the laser. light for recording information in
-3.5 the second test recording area passes, may extend outward
from an outer and of an area of the first information
recording layer corresponding to the second test recording
area by a length b', the length S' being represented by:
S' - d-tan(sin"1'(NA/n)) + $m
where bm is a maximum positional offset distance between the
first - information recording layer and the second
information recording layer.
The area of the first information recording layer,
through which the laser light for recording information in
the second test recording area passes, may extend outward
from an-. outer end of an area of the first information
recording layer corresponding to the second test recording
area by a length 5', the length 8' being represented by:
S` = d=tan(sin"1(NA/n)) + Sm
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where fin is a maximum positional offset distance between the
first information recording layer and the second
information recording layer.
An optical information recording method according
to the present invention is for an optical information
recording medium including a first information recording
layer on which information is to be recorded by laser light;
and a second information recording layer on which
information is to be recorded by the laser light which has
passed through the first information recording layer. The
first information recording layer includes at least one of
a reproduction-only area and a recording and reproduction
area. The second information recording layer includes a
test recording area. The optical information recording
method includes the steps of recording information, In.
advance, in an area of the first information recording layer,
through which the laser light for recording information in
the test recording area is to pass; and recording the
information in the test recording area after the step of
recording the information in advance.
The optical information recording method may.
further include a separation layer for separating the first
information recording layer and the second information
recording layer from each other. The area of the first
information recording layer, through which the laser light
for recording information in the test recording area passes,
may extend outward from an outer and of an area of the first
information recording layer corresponding to the test
recording area by a length 6, the length 6 being represented
by:
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$ = d-tan(sin'i(NA/n)),
where d is a distance in a thickness direction between, the
first information . recording layer and the second
information recording layer; n is a refractive index of the
separation layer; and NA is a numerical aperture of an
objective lens for focusing the laser light to the test
recording area.
The area of the first information recording layer,
through which the laser light for recording information in
the test recording area passes, may extend outward from the
outer end of the area of the first information recording
i5 layer corresponding to the test recording area by=a length
S', the length 8' being represented by:
d=tan(sin",1(NA/n)) + bf
where $m is a maximum positional offset distance between the
first information recording layer and the second
information recording layer.
The information which is recorded in advance may be
information obtained by modulating dummy information.
The step of recording the information in advance may
include the step of recording using a certification step.
An optical information recording method according
to the present invention is for an optical information
recording medium including a first information recording
layer on which information is to be recorded by laser light;
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and a second information recording layer on which
information is to be recorded by the laser light which has
passed through the first information recording layer. The
first information recording layer includes at least one of
a reproduction-only area and a recording and reproduction
area. The second information recording layer includes a.
test 'recording area. The optical information recording
method includes the. steps of determining whether an area
of the first information recording layer, through which the
laser light for recording information in the test recording
area passes, is an area of one of the reproduction-only area
and the recording and reproduction area which is an
unrecorded state or an area of the recording and
reproduction area which is in a recorded state; executing
test recording in the test recording area so as to obtain
a recording condition; and calculating an optimum recording
condition for the second information recording layer based
on the result of the determination and the obtained
recording condition.
The optical information recording medium may
further include a separation layer for separating the first
information recording layer and the second information
recording layer from each other. The area of the first
information recording layer, through which the laser light
for recording information in the test recording area passes,
may extend outward from an outer end of an area of the first
information recording layer,corresponding to the test
recording area by a length 8, the length 8 being represented
by:
S = d=tan (sin"1(NA/n)) ,
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where d is a distance in a thickness direction between the-
first information recording layer and the second
information recording layer; n is a refractive Index of the
separation layer; and NA is a numerical aperture of an
objective lens for focusing the laser. light to the second
recording and reproduction area.
The area of the first information recording layer,
through which the laser light for recording information* in
the test recording area passes, may extend outward from the
outer end of the area of the first information recording
layer corresponding to the test recording area by ,a length
s', the length by being represented by:
b' d=tan (sin-1(NA/n)) + &n
where &n Is a maximum positional offset distance between .thee
first information recording layer and the second
information recording layer.
The information for calculating the optimum
recording condition may be recorded in a specific area of
the first information recording layer and the second
information recording layer.
An optical information recording apparatus
according to the present invention is for an optical
information recording medium including a first information
recording layer on which information is to be recorded by
laser light; and a "second information recording layer on
which information is to be recorded by the laser light which
has passed through the first information recording layer.
The second Information recording layer includes a test
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recording area. The optical information recording
apparatus includes an interference area determination
section for determining an area of the first information
recording layer through which the laser light f or recording
information in the test . recording area passes; a
recorded/unrecorded state determination section for
determining-whether the area of the first information
recording layer, thrbugh which the laser light for
recording information in the test recording area passes,
is in a recorded state or in an unrecorded state; and a
recording section for recording a signal in the area of the
first information recording layer, through which the laser
light for recording information in the test recording area
passes, based On the results of the determination of the
interference area determination section and the
recorded/unrecorded state determination section.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 3. shows an external view of an optical
information recording medium according to the present
invention.
Figure 2 is a cross-sectional view of the optical
information recording medium according to the present
invention.
Figure 3 shows a format of a first information
recording layer and a second information recording layer
according to Example 1 of the present invention.
Figure 4 shows a format of a first information
recording layer and a second information recording layer
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of a comparative example.
Figure 5 shows the length of a light spot of the
first information recording layer (i.e., an area of the
first information recording layer, through which laser
light passes) according to the present invention.
Figure '6 shows a format of a first information
recording layer and a second information recording layer
according to a modified example of Example 1.
Figure 7 shows a format of a first information.
recording layer and a second information recording layer
according to Example 2-of the present invention..
Figure 8 shows a format of a first information
recording layer and a second information recording layer
according to Example 3 of the present invention.
Figure 9 is a block diagram of an optical
information recording apparatus for creating an optical
.information recording medium according to Example 3 of the
present invention.
25. Figure 10 shows a format of a first information
recording layer and a second information recording layer
according to Example.4 of the present invention.
Figure. 11 shows a format of a first information
recording layer and a second information recording layer
according to Example 5 of the present invention.
Figure 12 shows a format of a first information
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recording layer and a. second information recording layer
according to Example-6 of the present invention.
Figure 13. shows a format of a plurality of
information recording layers according to Example 7 of the
present invention.
Figure 14 shows a format of a first information
recording layer and a second information recording layer
according to Example 8 of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be
described by way of illustrative examples with reference
to attached drawings.
(Example, '.1)
This example relates to an optical information
recording medium with which accurate recording conditions
can be obtained by the test recording.
Figure 1 is an external view of an optical
information recording medium 100 according to the present
invention. Hereinafter, the optical disc 100 will be used
as a specific example of the optical information recording
medium 100.
Figure 2 is a cross-sectional view illustrating a
structure. of the optical information recording medium or,
the optical disc 100. The optical disc 100 has a multi-layer
structure. As shown in Figure 2, the optical disc 100
includes an incidence surface 110, a first information
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recording layer 120, a second information recording layer
130, and a separation layer 150 for separating the first
information recording layer 120 and the second information
recording layer 130 from each other.
The first information recording layer 120 and the
second information recording layer 130 are formed by
pre-forming a groove or a phase pit in a first substrate,
140 and a second substrate 145 respectively, and then
forming a protective layer, a recording layer, a reflective
layer and the like thereon. The resultant first substrate
140 and the resultant second substrate 145 are bonded
together with an ultraviolet-curable resin or the like, so
as to form the separation layer 150. The separation layer
150 separates the first information recording layer 120 and
the second information recording layer 130 from each other.
Laser light 170 is focused by an objective lens 160
and then is incident on the incidence surface 110. The laser
light 170 records information on the information recording
layers. Figure 2 shows a state where information is
recorded on the second information recording layer 130 by
the laser light 170 which has passed through the first
information recording layer 120.
Next, a format of the optical disc 100 used in this
example will be described.
Figure 3 shows a format of the first information
recording layer 120 and the second information recording
layer 130. Figure 3 shows the format in a radial direction
of the disc from the center of the optical disc 100. The
center of the optical disc 100 is represented by "0* in the'
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radial direction. The distance along the arrow labeled as
"radial direction" indicates distance from the center-of
the optical disc 100. The left side of the figure represents
the inner side of the optical disc 100, and the right side
of the figure represents the outer side of the optical disc
100. In Figure 3, it is assumed that laser light is directed
toward the optical disc 100 from the bottom portion of the
figure.
The first information recording layer 120 includes
a first reproduction-only area (ROM) 122 and a first
recording and reproduction area (RAM) 124. The first
recording and reproduction area 124 includes a first test
recording area (TEST) 126 and a first data recording area
(DATA) 128. In Figure 3, the first information recording
layer 120 includes the first reproduction-only area 122,
the, first test recording area 126, and the first data
recording area 128 in that order'from the inner portion
thereof.
The second information recording layer 130 includes
a second reproduction-only area (ROM) 132 and a second
recording. and reproduction area (RAM) 134. The second
recording and reproduction area 134 includes a second test
recording area (TEST) 136.and a second data recording area
(DATA) 138. An area 133 between the second
reproduction-only area 132 and the second test recording
area 136 is, for example, an unused area which has not been
used. In Figure 3, the second information recording layer
30- 130 includes the second reproduction-only area 132, the
unused area 133, the second test recording area 136, and
the second data recording area 138 in that order from the
inner portion thereof.
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In the first reproduction-only area 122 and the
second reproduction-only area 132, a phase pit. array
representing information is formed. In the first recording
and reproduction area 124 and the second recording and
reproduction area 134, grooves representing information
are formed.
In this specification, it is assumed that in a
reproduction-only area, information which does not need to
be rewritten, for example, information of the optical disc
itself or address information, is recorded. By contrast,
it is also assumed that in a recording and reproduction area,
information which has a high possibility of being rewritten
is recorded. Since different types of information are
recorded in the reproduction-only area and in the recording
and reproduction area, the information is recorded in
different forms in the reproduction-only area and in the
recording and reproduction area as described above. In the
reproduction-only area, information which does not need to
be rewritten is recorded. Therefore, such information is
recorded with a phase pit array, simultaneously with the
formation of the substrate. In the recording and
reproduction area, information which has a high possibility
of being rewritten is recorded. Therefore, information is
recorded in the form of a recording mark on the recording
layer which is formed on.the grooves.
In this specification, a test recording area is used
for performing test recording on the information recording
layer including the test recording area. A data recording
area is used for recording user data information.
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In this example, the first information recording-
layer 120 and the second information recording layer 130
are provided from the center of the disc substantially
parallel to each other and have substantially the same
length as each other.
Throughout . this specification,. for easier
understanding of the invention, when the optical
information recording medium includes two information
recording layers, the information recording layer which is
closer to the incidence side of the optical information
recording medium is referred to as the 'first information.
recording layer*, and the information recording layer which
is farther from the incidence side of the. optical
information recording medium is referred to as the 'second
information recording layer'. As described in detail below,
the number of the information recording layers of the
optical information recording medium is not limited to two.
The present invention is applicable to an optical
information recording medium having a plurality of
information recording layers.
Returning to Figure 3, the format of the optical
disc 100 will be described.
The first recording and reproduction area 124 of the
first information recording layer 120 extends from position
rl to an. outer periphery of the optical disc 100.
The second test recording area 136 of the second
information recording layer 130 extends from position r2
by distance a.
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The start point of the first recording and
reproduction area 124 is closer to the center of the disc
by length S than the start point of the second test recording
area 136. In this specification, a "start point" of an area
refers to the point in an area having the shortest distance
from the center of the disc, and a "termination point" of
an area refers to the point in an.. area having the longest
distance from the center of the disc-
Here, it is assumed that information is recorded in
the second test recording. area 136 in order to perform test
recording of the'second information recording layer 130.
The laser light 170 for recording information in the
second test recording area 136 passes through the first
information recording layer 120. Since the laser light 170
is focused after being incident, an area (light spot) 175
of the first information recording layer, through which the
laser light 170 passes, is larger than the second test
recording area 136. In this example, the optical disc 100
is structured such that the' first recording and
reproduction area 124 includes the area 175 of the first
information recording layer 120 through which the laser
light 170 passes for recording information in the second
test recording area 136. For this reason, the start point
of the first recording and reproduction layer 124 is closer
to the center of the disc, by length S than the start point
of the second test recording area 136. In Figure 3, only
the laser light 170 incident in a portion internal to the
second test recording area 136 is considered. The reason
is that, since in this structure, the first recording and
reproduction area 124 extends from the start point of the
first test recording area 126 to the outer periphery of the
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disc, it is not necessary to consider the laser light 170
incident in a portion external to the second test recording.
area 136.
The length of the area 175 of the first information
recording layer 120, through which the laser light 170 which
is to be focused in the second test recording area 136 passes,
equals 8 + a + 8. Namely, the area 175 includes an area
corresponding to the second test recording area 136 having
the length a'and two areas respectively extending from an
inner. end and-an outer end of the above-mentioned area
toward the center of the disc and the outer periphery of
the disc, each extending area having length 8. As described
above, such a size of the area 175 results from,the fact
that the diameter of the spot of the laser light 170 at the
first information recording layer 120 is greater than that
at the second information recording layer 130. In the case
where the first recording and reproduction area 124 and the
second test recording area 136 are located such that 'the
first recording and reproduction area 124 includes at least
the area 175, the laser light 170 passes through only the
first recording and reproduction area 124 when passing'
through the first information recording layer 120 in the
test recording performed using the second test recording
area 136.
As described above, the first recording and
reproduction area 124 and the second test recording area
136 are located such that the laser light 170 passes through
only-the first recording and reproduction area 124 when
passing through the first information recording layer 120
in the test recording performed on the second test recording
area 136. The reasons are as follows.
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A recording and reproduction area and a
reproduction-only area are formed in different forms.
Therefore, the light transmittance of the recording and
reproduction area may sometimes be different from the light
transmittance of the reproduction-only area. When laser
light passes through both the reproduction-only area and
the recording and reproduction area in this case, a
component of light passing through the reproduction-only
area and reaching the second information recording layer
and a component of light passing through the recording and
reproduction area and reaching the second information
recording layer will have different amounts.
The light transmittance of an unrecorded area in the
recording and reproduction area can be considered to be
equal to the light transmittance of the reproduction-only
area. However, when the recording and reproduction area
has information recorded therein, the light transmittance
of a recorded area in the recording and reproduction area
is different' from the light transmittance of the
reproduction-only area. Accordingly, when information is
recorded in the recording and reproduction area of the first
information recording layer, the light transmittance is
different between the reproduction-only area 122 and the
recording. and reproduction area 124 of the first
information recording layer 120.
In a recording and reproduction area, a recording
mark tin an amorphous state.) is formed. When the recording
mark is formed, the light transmittance of the recording
and reproduction area is raised in some cases and is reduced
in other cases. Hereinafter, the case where the light
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transmittance is rained will be described. In this case,'
the amount of light transmitted through the recording and
reproduction- area 'is larger than amount of light
transmitted through the reproduction-only area.
For comparison, Figure 4 shows a format of an
optical disc 400 in which a first information recording
layer and a second information recording layer have the same
format.
The optical disc 400 includes a first information
recording layer 420, a second information recording layer.
430, and a separation layer 450 for separating the first
information recording layer 420 and the second. information.
recording layer 430 from each other.
The first information recording layer 420 includes:
a first reproduction- only area (ROM)- 422 and a first
recording and reproduction area (RAM) 424. The first
recording and reproduction area 424 includes'a first test
recording area'(TEST) 426 and a first data recording area
(DATA) 428.
The second information recording layer 430 includes
a second reproduction-only area (ROM) 432 and a second
recording and reproduction area (RAM) 434. The second
recording and reproduction area 434. includes a second test
recording area (TEST) 436 and a second data recording area
(DATA) 438.
In this comparative example, the format of the first
information recording layer 420 is the same as that of the
second information recording layer 430. Therefore, the
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start point ri' of the first recording and reproduction area
424 is the'same as the start point r2' of the second test
recording area 436.
In this case, when laser light 470 is Incident on
the innermost ,portion of the second test recording area 436
(i.e., the left end of the second test recording area.436
as shown in Figure 4) for test recording of the second
information recording layer 430, half of the laser light
470 incident on the first information recording layer 420
is transmitted through the first reproduction-only area
422.
As a result, the amount of laser light 470 passing
through the first reproduction-only area 422 and reaching
the second information recording layer 430 is different
from the amount of laser light 470 passing through the first
recording and reproduction area 424 and reaching the second
information recording layer 430.. Therefore, accurate test
recording cannot be performed. For example, when the light
transmittance of the recording and reproduction area is
higher than the light transmittance of the
reproduction-only area, recording power which. is greater
than the recording power of the laser light passing through
the reproduction-only area is determined to be the desired
recording power.
Accordingly, when test recording is performed using
the innermost portion of the second test recording area 436
(i.e., the left end of the second test recording area 436
in Figure 4) in order to obtain the desired recording power,
recording power which is greater than the appropriate
recording power is provided as the result of the test
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recording result. Therefore, actual data is recorded at'
excessively high recording power.
Moreover, the amount of the laser light 470 reaching
the second information recording layer 430 varies in=
accordance with the ratio of the laser light 470 transmitted
through the first reproduction-only area 422 with respect
to the entire laser light 470 used for recording information
in the second test recording area 436. As a result, the
test recording result varies in accordance with the
position of the second test recording area 436 in which
information is recorded.
By contrast, with the format according, to this
example shown in Figure 3, the laser light 170 is. not
influenced by the first reproduction-only area 122
regardless of the position in the second test recording area
136 at which test recording is performed. Accordingly,
accurate recording conditions are obtained by the test
20. recording.
Hereinafter, with reference to Figure 5, expansion
of the light spot 175 on the first information recording
layer 120 will be described in. detail. Figure 5 shows the
length of the light. spot' 175 on the first information
recording laser 120 when the laser light 170 is focused on
the second information recording layer 130. Here, for
simpler explanation, the laser light 170 is focused onto
a focal point 172 on the second information recording layer
30130. In this state, the angle 6 at which the laser light
170 is focused onto the focal point 172 is:
9 - sin-'(NA/n).
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Where the distance in the thickness direction of the
disc between the first information recording layer 720 and
the second information recording layer 130 is d, the
numerical aperture of the objective lens 160 is NA, and the
refractive index of the. separation =layer. 150 is n, the
radius 8 of the light spot 175 on the first information
recording layer 120 is represented by:
S d=tan9 = d=tan (sin"'. (NA/n)) .
From this, as long as the start point of the first
test recording area 126 in Figure 3 is away from the start
point of the second test recording area 136 by at least
length 8 represented by the above expression, the first
recording and reproduction area 124 includes the light spot
175 of the laser light. 170 on the first information
recording layer 120. In this case, accurate recording
conditions can be obtained by the test recording.
As described above, the optical information
recording medium 100 according to this example is
structured such that the first recording and reproduction
area 124, includes the area 175 of the first information
recording layer 120 of the laser light 170 for recording
information in the second test recording area 136 passes.
Therefore, accurate recording conditions can be obtained
by the test recording.
In Figure 3, the area between the second
reproduction-only area 132 and the second test recording
area 136 Is the unused area 133. The present invention is
not limited to this.
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For example, as shown in Figure 6, -the unused area
133 may be replaced with a third data recording area 137.
In this. case,. the length of the data recording area 137 is
at least equal to length 8. An optical disc 600 shown in
Figure 6 has the same format as that of the optical disc
100 shown in Figure 3 except that the unused area 133 is
replaced with the third data recording area 137. Such a
format can expand the data recording area compared to that
of the disc 100 shown in Figure 3.
(Example 2)
. In this example, a case where the center of the two
information recording layers are offset with respect to
each other will be described.
In actual production of a multi-layer recording
medium, a plurality of information recording layers may be
sometimes positionally offset with respect to each other
when the information recording layers are bonded together.
When the start points of the test recording areas are. offset
with respect to each other due to*the positional offset
between the information recording layers, the length 8
considered in Example I is not sufficient. In this example,
the effect of the present invention is provided even when
the distances of the two information recording layers from
the center of the disc are different from each other.
Figure 7 shows a format of an optical disc 700 in
which. a first information recording layer 720 and a second
information recording layer 730 are offset with respect to
each other by 8m.
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The optical disc 700 includes the first information
recording layer 720, the second information recording layer
730, and a separation layer 750 for separating the first
information recording layer 720 and the second information
recording layer 730 from each other.
The first information recording layer 720 includes
a first reproduction-only area (ROM) 722 and a first
recording and reproduction area (RAM).724. The first
recording and reproduction area 724 includes a first test
recording area (TEST) 726 and a first data recording area
(DATA) 728. In Figure 7, the first information recording
layer 720 includes the first reproduction-only area 722,
the first test recording area 726, and the first data
recording area 728 in that order from the inner portion
thereof.
The second information recording layer 730 includes
a second reproduction-only area (ROM) 732 and a second
recording and reproduction area (RAM) 734. The second
information recording layer 730 may include an unused area
733. The second recording and reproduction area 734
includes a second test recording-area (TEST) 736 and a
second data recording area (DATA) 738.' In Figure 7, the
second information recording layer 730 includes the second
reproduction-only area 732, the unused area 733, the second
test recording area 736, and the second data recording area
738 in that order from the inner portion thereof.
In this figure, the offset 8' between the start
points of the first recording and reproduction area 724 and
the second test recording area 736, the offset 8' being
defined from the center of the disc, is represented by:
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S' = r2 - rl S + Sm d=tan(sin'i.(NA/n)) + Sm.
This represents a value obtained by adding the
length 8 of the light spot 725 on the first information
recording layer 720 described in Example 1 with the length
3m of the positional offset between the first information
recording layer 720 and the second information recording
layer 730.
Accordingly, as long as the start of the first
recording and reproduction area 724 is away from the start
of the second test recording area 736 by at least the length
3' represented by the above expression, the first. recording
and reproduction area 724 includes a light spot 775 on the
first information recording layer 720, through which laser
light 770 passes, even when the first information recording
layer 720 and the second information recording layer 730
are positionally offset with respect to each other by the
length 3m.
Considering the difference in the distances of the
first information recording layer 720 and the second
information recording layer 730 from the center of the disc,.
it is necessary that the first recording and reproduction
area 724 includes the area .775. Here, the area 775 is an
area of the first information recording layer 720 through
which the laser light 770 used for recording information
on the second test recording area 736 passes. The length
of the area 775 needs to be at least S' + a + S'. Namely.
the area 775 includes an area corresponding to the second
test recording area 736 having the length a and two areas
respectively extending from an inner end and- an outer and
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of the above-mentioned area toward the center of the disc
and the outer periphery of the disc, each extending area
having length 81. In the came where the first recording and-
reproduction area 724 and the second test recording area
736 are located such that the first recording and
reproduction area 724 includes the area.775, accurate
recording conditions can be obtained by the test recording.
(Example 3)
In this example, a case where the area of the first
information recording layer, through which laser light used
for recording information in the test recording area of the
second information recording layer passes, is a recorded
state area will be described.
Figure 8 shows a format of an optical disc 800
according to this example.
The optical disc 800 includes a first information
recording layer 820, a second information recording layer
830, and a separation layer 850 for separating the first
information recording layer 820 and the second information
recording layer 830 from each other.
The first information recording layer 820 includes
a first reproduction-only area 822 and a first recording
and reproduction area 824. The first. recording and
reproduction area 824 includes a first test recording area
826 and a first data recording area 828. In Figure 8, the
first information recording layer 820 includes the first
reproduction-only area 822, the first test recording area
826,' and the first' data recording area 828 in that order
from the inner portion thereof.
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The second information recording layer 830 includes
a second reproduction-only area 832 and a second recording
and reproduction area 834. The second recording and
reproduction area 834 includes a second test recording area
836 and a second data. recording area 838. An area 833
between the second reproduction-only area 832 and the
second test recording area 836 is, for example, an unused
area which has not been used. In Figure 8, the second
information recording layer 830 includes the second
reproduction-only area 832, an unused area 833, the second
test recording area 836, and the second data recording area
838 In that order from the inner portion thereof.
In the optical disc 800, the first recording and
reproduction area 824 includes a recorded state area 875
of the first information recording layer 820. Laser light
870, used for recording information in the second test
recording area 836, passes through the recorded' state area
875. The recorded state area- 875 is entirely in a recorded
state. The length of the recorded state area 875 is 8 + a
+ 8. Namely, the recorded state area 875 Includes an area
corresponding to the second test recording area 836 having
the length a and two areas respectively extending from an
inner and and an outer end of the above-mentioned area
toward the center of the disc and the outer periphery of
the disc, each extending area having length 8.
The recorded state area 875 is formed by recording
information in the entirety of the recorded state area 875
of the first recording and reproduction area 824, for
example, before the second test recording area 836 is used.
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Owing to such a structure, onto whichever position
of the second test recording area 836 the laser light 870
may be focused, the light transmittance of the area of the
first recording and reproduction area 824, through which
the laser light 870 passes (i.e., area 875), can be uniform.
The light transmittance varies depending on whether
information is recorded or not in the recording and
reproduction area 824. Since the area 875 is entirely in
a recorded state, the light transmittance is uniform.
Accordingly, as long as information is recorded in the
recorded state area 875 shown in Figure 8, the amount of
the laser light 870 reaching the second test recording area
836 is uniform when test recording is performed on the
second test recording area 836. As a result, accurate
i5 recording conditions can be obtained.
In this example, when the first information,
recording layer 820 and the second information recording
layer 830 are positionally of feet with respect to each other,
the length of the recorded state area 875 may have the length
S' + a + 8! as described in Example 2.
The information to be recorded in the recorded state
area 875 may be information obtained by modulating data
Information or information.,obtained by modulating dummy
information.
It is preferable to record information in the
recorded state area 875 at the time of certification after
the optical disc is produced. Since the recording apparatus
does not need to perform this step, the start time when a
new optical disc is mounted on the recording apparatus can
be shortened.
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Next, an optical recording apparatus for recording
information on the optical information recording medium
according to this example will be described.
Figure 9 shows an optical information recording
apparatus 900 for, creating the optical information
recording medium according to this example'. Hereinafter,
an operation of the optical information recording apparatus
900 will be described with reference to Figure 9.
The optical information recording apparatus 900.
includes a spindle motor 907 for rotating the optical disc
800 and an optical head 903 including a laser source (not
shown) and focusing laser light to a desired'position of
an information recording layer of the optical disc 800. The
entire operation of the optical information recording
apparatus 900 is controlled by a system control section 901.
It is not intended that the recorded state area- 875 of the
optical disc 800 in in a completely recorded state at this
point.
The optical information recording apparatus ' 900
further includes a recording section 902 for modulating the
light intensity of the laser source in the optical head 903
based on information obtained by modulating data
information, and a reproduction section 904 for performing
waveform processing of .a reproduction signal based on the
light reflected by the optical disc 800 so as to demodulate
reproduction information. The optical information
recording apparatus 900 also includes an interference area
determination section 905 for determining whether or not
a- given area of the first information recording layer 820
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is an area which can be an optical path of'the laser light
870 for recording information in the second test recording
area 836 (i.e., whether or not the given area is the area
875 through which the laser light passes for recording
information in the second test recording area 836), and a
recorded/unrecorded state determination section 906 for
reproducing the information in the area 875 through which
the laser light passes for recording information in the
second teat recording area 836 and then determining whether
the area 875 is in a recorded state or an unrecorded state
based on the reproduction result.
Hereinafter, with reference to Figures 8 and 9,
operation of the optical information recording apparatus'
900 according to this example will be described. First,
the system control circuit 901 rotates the spindle motor
907, and the optical head 903 focuses the laser light 870
onto the first information recording layer 820 on the
optical disc 800 'so as to reproduce information on the first
information recording layer 820. Based on address
reproduction information from the reproduction. section 904,
the interference area determination section 905 determines
whether the area, in which information is being reproduced,
is the area 875 or not. Based on the determination result,
the system control section 901 seeks for the optical head
903 up to a certain area in the area 875 and reproduces
information in the certain area of the area 875.
Based on the reproduction information from the
reproduction section 904, the recorded/unrecorded state
determination section 906 determines whether the track in
the certain area in the area 875, in which information is
being reproduced, is in a recorded state or an unrecorded
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state. When the recorded/unrecorded state determination
section 906 determines that the track is in an unrecorded
state, some information is recorded in the track in the
certain area in the area 875 so as to place the certain area
in the area 875 into a recorded state. When the
recorded/unrecorded state determination section 906
determines that the track is in a recorded state, it is
confirmed that the certain area in the area 875, in'which
information is being reproduced, is already in a recorded
state. This operation is performed for the entirety of the
area 875.
In this manner, the area 875 is entirely placed into
a recorded state, and thus acts as a recorded state area.
Onto whichever position of the second test recording area
836 the laser light 870 may be focused, the light
transmittance of the area 875 of the first information
recording layer 820, through which the laser light for
recording information in the second test recording area 836
passes, can be uniform. Accordingly, whichever portion of
the second test recording area 836 of the second information
recording layer may be used for test recording, the amount .
of the laser light reaching the second test recording area
836 is the same. Thus, accurate recording conditions can
be obtained.
(Example 4)
In Example 3, an operation for placing the area 875,
of the first information recording layer, through which the
laser light for recording information in the second test
recording area 836 passes, into a recorded state area was
described. In this example, a specific example of an
operation for placing the entirety of the area of the first
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information recording layer, through which the laser light
for recording information in the second test recording area
passes, into an unrecorded state will be described.
Figure 10 shows a format of an optical disc 1000
according to Example 4.
The optical disc 1000 includes a first information
recording layer 1020, a second information recording layer
10' 1030, and a separation layer 1050 for separating the first
information recording layer 1020 and the second information
recording layer 1030 from each other.
The first information recording layer 1020 includes
a first reproduction-only area 1022 and a first recording
and reproduction area 1024. The first recording. and
reproduction area 1024 includes a first test recording area
1026 and a first data recording area 1028. In Figure 10,
the first information recording . layer 1020 includes the
first reproduction-only area 1022, the first test recording
area 1026, and the first data recording area 1028 In that
order from the inner portion thereof.
The second information recording .layer 1030
includes a second reproduction-only area 1032 and a second
recording and reproduction area 1034. The. second recording
and reproduction area 1034 includes a second test recording
area 1036 and a second-data recording area 1038. An area
1033 between the second reproduction-only area 1032 and the
second test recording area 1036 is, for example, an unused
area which has not been used. In Figure 10, the second
information recording layer 1030 includes the second
reproduction-only area 1032, the unused area 1033, the
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second test recording area 1036, and the second data
recording area 1038 in that order from the inner portion
thereof.
In the optical disc 1000, the.first recording and
reproduction area 1024 includes a unrecorded state area
1075 of the first information recording layer 1020. Laser
light 1070; used for recording information in the second
test recording area 1036, passes through the unrecorded
state area 1075. The unrecorded state area 1075 is entirely
in an unrecorded state. The length of the unrecorded state
area 1075 is 8 + a +'8. Namely, the recorded state area 1075.
includes an area corresponding to the second test recording
area 1036 having the length a and two areas respectively
extending from an inner end and an outer end of, the
above-mentioned area toward the center of the disc and the
outer periphery of the disc, each extending area having
length 8.
As shown in Figure 10, the area, of the first
recording and reproduction area 1024 including the area
corresponding to the second test recording area 1036 having
the length a and two areas respectively extending from an
inner and and an outer end of the above-mentioned area
toward the center of .the disc and the outer periphery of
the disc, each extending area having length 8 (1. a. , the area
of the first information recording layer 1020 having the
length of 8 + a + 8) is in an unrecorded state at the time
of test recording.
The information for calculating optimum recording
conditions based on the result of the test recording may
be recorded in an arbitrary area of the first information
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recording layer 1020 and the second-information recording
layer 1030. In this case, the information for calculating
the optimum recording conditions are, for example,
information for multiplying the recording conditions in an
unrecorded state by a.certain coefficient based on, for
exaflple, the difference in the amount of transmitted light
between the unrecorded state and the recorded state. In
this example, the entirety of the area of the first
information recording layer 1020, through which the laser
light for recording information in the second test
recording area 1036 passes, is in an unrecorded state.
Accordingly, the recording conditions obtained in such a
circumstance have a possibility of not being optimum for
recording information in the second test recording area
1038 using the laser light which has passed through the
first recording information recording layer 1020 having
information recorded thereon.
Hereinafter, a specific example of an operation for
multiplying the recording conditions in an unrecorded state
by a 'certain coefficient based on the difference in the
amount of transmitted.light between the unrecorded state
and the recorded state will be described.
In the case of an optical disc in which the amount
of transmitted light in a recorded state is s times the
amount of transmitted light in an unrecorded state, where
the optimum recording power obtained by performing test
recording in an unrecorded state is Pm, the optimum
recording power Pk in a recorded state can be calculated
as follows.
Pk Pm/s
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Here, "s` is defined as the transmittance
correction coefficient. By such a calculation, even when
information is not recorded in a specific area of the, first
information recording layer 1020 in advance, the optimum
recording power in the case where the.area of the first
information recording layer 1020, through which the laser
light passes, is in a recorded state can be estimated. In
the case where it is time-consuming to form the recorded
state area 87S in the first information recording layer 1020
-as in Example 3, the optimum recording conditions can be
calculated as in this example, instead of directly
obtaining the optimum recording conditions as in Example
3.
In the case where there is a possibility that the
first information recording layer 1020 and the second
information recording layer 1030 in this example are
positionally offset, with respect to each other, it. is
preferable to keep the unrecorded state area 1075 having
the length 5' + a + S' unrecorded at the time of test
recording as described in Example 2.
In this example, it is more preferable to record the
transmittance correction coefficient s for determining the
optimum recording power in a specific area in the optical
disc 1000 (for example, the first reproduction-only area
1022 or the second reproduction-only area 1032). In this
case, even when the transmittance correction coefficient
s is different among different optical discs, the optical
disc recording apparatus can immediately learn the
coefficient when an optical disc is mounted on the optical
disc recording apparatus. Therefore, the time, required to
CA 02687697 2009-04-14
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46 - P26109
start actually recording information can be shortened.
In this example, the unrecorded state area at the
time of test recording may be' a recording prohibited area
where-information is never recorded. Alternatively, the
unrecorded state area may be a mirror area which does not
have any guide grooves for tracking servo control.
(Exampl'e 5)
In Examples 1 through 4, the recording and
reproduction area of the first information recording layer
includes a light spot of the laser light. The present
invention is not limited .to such a format. In this example,
a format where the reproduction-only area of the first
information recording layer includes a light spot of the
laser light will be described..
Figure 11 shows a format of an optical disc 1100
according to Example 5.
The optical disc 1100 includes a first information
recording layer 1120, a second information recording layer
1130, and a separation layer 1150 for separating the first
information recording layer 1120 and the second information
recording layer 1130 from each other.
The first information recording layer 1120 includes
a first reproduction-only area 1122 and a first recording
and reproduction area 1124. The first recording and
reproduction area 1124 includes a first test recording area
1126 and a first data recording area 1128. In Figure 11,
the first information recording layer, 1120 includes the
first reproduction-only area 1122, the first test recording
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area 1126, and the first data recording area 1128 in that
order from the inner portion thereof.
The second information recording layer 1130
includes a second reproduction-only area 1132, a third
reproduction-only area 1133, and a second recording and
reproduction area 1134. The second. recording, and
reproduction area 1134 includes a second test recording
area 1136 and a second data recording area 1138.. In Figure
11, the second information recording layer 1130 includes
the second reproduction-only area 1132, the second test
recording area 1136, the third reproduction-only area. 1133,
and the second data recording area 1138 in that order from
the inner portion thereof.
As shown in Figure 11, the first reproduction-only
area 1122 of the first information recording layer 1120 is
structured so as to include an area (light spot) 1175
through which laser light 1170 for recording information
in the second test recording area 1136 passes. The length
of the area 1175 is 8 + a + 6. Namely, the.area 1175, includes
an area corresponding to the second test recording area 1136
having the length a, and two areas respectively extending
from an inner end and an outer end of the above-mentioned
area toward the center of the disc and the outer periphery
of the disc, each extending area having length 6. Thus, at
whichever position of the second test recording'area 1136
test recording may be performed, the laser light for
recording information in the second test recording area
1136 is the laser light which has passed through the first
reproduction-only area 1122. As a result, the recording
conditions are prevented from being dispersed depending on
.the position at which the test recording is performed.
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In this example, as described in Example 4, it is
more preferable to calculate the optimum recording
conditions based on the result of the test recording. Thus,
the optimum recording conditions for the case where the
laser light passes through the first recording and
reproduction area 1124, which is in a recorded state with
a recording mark array being formed, can be estimated.
In the case where there is a possibility that the
first information recording layer 1120 and the second
information recording layer 1130 are positionally offset
with respect to each other, the first reproduction-only
area 1122 is located so as to have the length 8' + a +
which is the length of the area 1175 of the first Information
recording layer 1120, as described in Example 2.
(Example 6)
In Examples 1 through 5, information is recorded in
the test recording area of the second information recording
layer in order to perform test recording of the second
information recording layer. When data is recorded in the
recording and reproduction area of. the second information
recording layer, as well as at the time of test recording
described in Examples 1 through 5, there is a possibility
of the signal quality for reproducing the recorded signal.
being lowered. The reason is that when the laser light used
for recording passes through both the reproduction-only
area and the recording and reproduction area, the amount
of laser light reaching the recording and reproduction area
of the second information recording layer is different
depending on which one of the above two areas the laser light
has passed through. As a result, accurate recording cannot
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be performed.
In this example, a specific example of recording
information in the recording and. reproduction area of the
second information recording.layer will be described.
Figure 12 shows a format of an optical disc 1200
according to Example 6.
The optical disc 1200 includes a first information
recording layer 1220, a second information recording layer
1230, and a separation layer 1250 for separating the-first,
information recording layer 1220 and the second information
recording layer 1230 from each other.
The first information recording layer'1220 includes
a first reproduction-only area 1222 and a first recording
and reproduction area 1224. In Figure 12, the first
information recording layer 1220 includes the first
reproduction-only area 1222 and the first recording and
reproduction area 1224 in that order from the inner portion
thereof.
The second information recording layer 1230
includes a second reproduction-only area 1232 and a second
recording and reproduction area 1234. In Figure 12, the
second information recording layer 1230 includes the second
reproduction-only area 1232 and the second recording and
reproduction area. 1234 in that order from the inner portion
10, thereof.
As shown in Figure 12, the first reproduction-only
area 1222 is preferably smaller than the second
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reproduction-only area 1232 of the second' information.
recording layer 1230.
In Figure 12,-the start point of-the first, recording.
and reproduction area 1224 is located closer. to. the center,
of the disc than the start point' of the second- recording.,,
and reproduction area 1234 by length 8. .'Owing,. to. such a
-structure, * in whichever portion of the, second recording. And
reproduction. area 1234 .information may be., recorded;.. the
first .recording 'and reproduction area 1224: includes an:,area
1275 of the first information recording .layer 1220:,through
which the laser light for recording information:.. in the
second recording and reproduction area' 1234 -passe a.,
Therefore, the second recording and. reproduction area 1234
is only influenced by the first recording and reproduction
area 1224 and is not influenced by the.. 'first
reproduction.-only area 1222. Thus, information can be
accurately recorded in the second recording and
reproduction: area. 1234.
In the case where there is a possibility that`,-the
first information recording layer 1220 and- the -second
information recording layer 1230 are positionally offset
with respect to each other, the start point of the first
recording and reproduction area 1224 and the start point
of the second recording and -reeproduction area 1234 are
preferably offset with respect to each. other by 6' as
described in Example 2.
.30 In Figure 12, the. size of the :first.
reproduction only area 1222.may be zero. In this case. it.
is not necessary, to form a phase pit for the first
reproduction-only area 1222 at the time'of production of
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the first information recording layer 1200. Thus, the .
production process of .the disc. can be simplified.
(Example 7)
In Examples 1 through, 6, there are two information
recording layers.. The present invention is not - limited = t'o
this.. According to , the' present invention, . the number of,''
information recording layers.may-be.three or more.
.:Figure 13 shows=a-format of an optical disc 1300
according to-Example 1 of the present invention.
The optical disc 1300 is obtained by expanding the
optical disc in Example 1, and has a different format from
that. of the optical disc-in Example 1. The-optical disc
1300. includes- N number of information- recording layers. In
Figure 13, among the N number` of information recording'
layers, three information recording layers i, j and k each.:.
have a reproduction area in ,order to obtai'n' accurate
recording conditions by. the test, .recording.
In this example, a first information recording
layer' 1310 is the i'thlayer, a second information recording
layer 1320 is the j'th layer, a third information recording
layer 1330. is the k'th layer, from the laser incidence side
of the disc. The distance between the first information
recording layer 1310 and the second informationn . recording
layer. 1320 is dij, the distance between the second
information recording layer 1320 and* the third information
recording -layer 1330 is d jk, 'and distance between the first
information'recording-layer 1310 and the third information .
recording. layer 1330 is dik.
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The first information recording'layer.1310 includes
a first reproduction-only, area 1312and-a first recording
and reproduction area j314." The' first. recording and'.
reproduction area 1314. Includes a first test recording area
1316 and:a first data recording area..1318:
The second information recording. layer 1320'.
includes a second reproduction-only, area 1322 and a second
recording and reproduction area 1324. The second recording
10' and reproduction area 1324 includes a second.test .recording,'.'.
area.1326 and a.second data recording area 1328
The third information recording layer 1330. includes..,
a third ' reproduction-only area .1332 and a third recording'
and reproduction area 1334. The third recording, and..
reproduction area 1334 includes a third test recording area
1336 and .a third data recording area .1338.
In this case, the start point of the first recording
and reproduction, area .1312 is at least Sij away from the.
start point of the second test recording- area 1326, and is-
at least Sik away from = the start. point . of the, third ' test
recording area 1336. The start point of the second.
recording and reproduction area 1324 is at least $jk away
from. the start point of the third- test recording area. 1336.
Here,
Si j = di j.=tan (sin-1(NA/n))
Sik = dik=tan(sin"1(NA/n)), and
.30 jk djk-tan(sin'l(NA/n));
where NA is the numerical aperture of an objective
lens for focusing laser light 1370,. and n is the refractive
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index of the separation layer between the first information
recording layer 1310 and the second information recording*
layer 1320 . and, ofthe.separation layer between the second
information.recording= layer 1320 and the, third information :
recording-layer 1330.
Owing to .such. a structure, the laser light 1370.:for.
recording information in'the second teat recording area.
1326 passes through only the first recording and'
reproduction area 1314 when passing through the. first..
information recording, layer, 1310... The laser -light .1370for
recording information in the third test recording area 1336
passes through only the first, recording and reproduction
area 1314, when passing through the first information
recording layer 1310 and only the second recording ' and
reproduction area 1324 when passing. through the second
information recording layer 1320. . '
Even when the information recording. layer as a
target is, for example, between, the first information
recording layer 1310 and the second information recording
layer 1320 as in this example 'or at an arbitrary position.,
substantially the same effect an that in Example 1 is
provided-, as long as the second information recording layer
1320. Is. farther from the incidence surface than the first,
information recording layer 1310,' and an area of the. first
information recording. layer .1310, through which the laser .
light 1370 for recording information in the second test
recording area 1326 passes, is entirely a recording'and.
reproduction area..
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(Example 8)
Figure 14 ' shows a format of an optical-disc 1400
according to. Example s of the present invention
The optical disc '1400' includes. a first information'
recording layer 1420, 'a second information 'recording layer
1430. and.a separation layer 1430, for -separating the first.
information recording layer 1420 and the second information
recording layer 1430 from each other.
.10
The first information recording layer.1420 includes
a -first reproduction-only area 1422, A. first recording and
reproduction area 1424 and a second reproduction-only, .area
1429. The first recording and reproduction, area 1424
'includes a first test recording area 1426 and a . first 'data
recording area 1428.. In Figure =14 , the first information
recording-layer. 1420. includes the-first test'recording area
1426, the first reproduction-.only area 14.22, the first data
recording area 1428, and the second reproduction-only, .area' .
- 1429 in that order from the inner portion thereof . The first
information recording layer 1420 includes a.first lead-in
area 1425-and a first lead-out area 1427. The first lead-in
area '1425 includes the first test recording area 1426 and-
the first reproduction-only area 1422. The first lead-out ..
area 1427 includes the second reproduction-only area: 1429.
The second information recording layer 1430
includes a third. reproduction-'only area 1432, a second
,-recarding and reproduction area 1434, a fourth
reproduction-only area 1433, and a fifth reproduction-only .
area 1439. The second recording and reproduction area 1434
includes a second test recording area.1436 and a second data
..recording area 1438. In Figure 14, the second information ,
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recording layer 1430 includes the third reproduction-only.
area 1432, the second test recording' area 1436, the fourth
reproduction-only area 1433, the second data recording area.
1438, and the fifth reproduction-only.area1439 in that
S order from the inner portion thereof The second
,'information recording layer 1430 includes a second. lead-in
.`area 1435 and a second lead-out area 1437.. The second
lead-in. area 1435 includes the third ' reproduction-only area
1432,'the' second, test recording area 1436, and. the fourth
reproduction-only area 1433. The second lead-out area 1437
includes the fifth reproduction-only', area . 1439..
In this example, when priority is put "on easy
management. of the optical disc 1400, 'it is preferable to
have the format shown in Figure 14 in which 'then first, data
recording area. 1428 . and' the second data recording area 1438
have an equ4 size. The optical disc 1400 includes. the first
lead-in area 1425 and the second lead-in area 1435
:internally to the first data recording. area 1428 and the,
second data recording area 1438, respectively. The optical.
disc 1400. also includes the first lead-out area 1427 and,
the second., lead-out area ' 1439 externally to the first . data
recording area 1428 and the second data recording area 1438,
respectively. The first test recording area 1426 is located
internally to the first lead-in area 1425, and the second
test recording area'1436 is located internally to the second,
lead-in area 1435.
The first test recording area 1426'and the second..
. test recording area 1436 are . positionally offset with .
respect to each, other by length 6 or more. The . first '
reproduction-only area 1422.includes a non-uniform-light
prevention area 1475 of the first information recording
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56 P26109
layer 1410.'through which laser light 1470 for recording'
information - in the second test recording area: 1436 passes.
The length of the area 1475 is represented by 6 + a + 8. ' The
non-uniform light prevention area 1475-prevents. -the= laser.
5. light 1470 incident thereon from transmitting therethrough,
in a non-uniform.shape.
The non-uniform, light prevention area 1475 in, 1 ,or
example, a reproduction-only area.
Alternatively,, the non-uniform light-.:prevention
area 1475 may be a recording prohibited area or a mirror
area. Owing to such a structure, at whichever position of
the second test recording area 1436 test recording may be
....15 performed, the obtained recording conditions. -are, not
dispersed. Moreover, owing'to such a structure, the first
lead-in-area 1425 of the first information recording- layer.
1420' and. the second lead-in area. 1435 of the second
information recording layer 1430can have-identical start.
2.0= points, termination points and capacities The first-data
recording area' 1,425. of the first information recording
layer.1420 and.the second data recording area.143.8 of the
second' information recording layer 1430 can. haven identical
start points, termination points and capacities.. The first.
25 lead-out area 1427 of the first information recording layer
1420 and the second lead-out area 1437 of the second
information recording layer 1430 can have. identical: start
points,. termination points and capacities. Therefore,
defect management. and recording information management of.
30 the optical disc 1400 are advantageously easy:
Substantially the seine effect is'provided when the first.
test recording area 1426, is located-in the- first lead-out,
.' area 1427 and the second test recording area 1436 is located
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in the second lead-out area 1437.
The positions of the areas and the shape of the disc
used in the above examples are not limited to. those
5. described'' above, and, may be of any appropriate form in
and:
accordance with the' medium itself or the. recording
reproduction. apparatus.
INDUSTRIAL-APPLICABILITY
.10
As described' above,.'according to an. -optical
information recording medium of the present invention, an
area of the first information recording. layer, through..
which laser light passes, :is entirely placed into a recorded
15 state or an unrecorded state at the'time of test recording
of the second information recording layer. Therefore,
accurate recording conditions can be obtained by. the test
recording.
20 According.,to an optical information recording
medium. of . the present invention, an area . ' of . the first
information recording layer, through which. laser light
passes, is entirely placed into a reproduction-only,area
or a recording and reproduction area at the time of test
25 recording. of the second information recording layer.
Therefore, accurate' recording conditions can be'obtained
by the test. recording. '.
According to an optical information recording:
-30' medium of the present invention, the reproduction-only area
of the first information recording layer is made smaller
than the reproduction-only area of the second information
recording layer. Therefore, information can be accurately
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recorded anywhere in-the recording and reproduction ' area
of the second information recording layer:.
According to. an optical information. recording.
medium of the present invention, when recording information
in the recording and reproduction, area of the. second '-
information recording .layer, an area of the first.
information recording layer, through which laser light
passes,, is entirely.' _ placed into a reproduction-only .area
or. a. recording and. reproduction area. Therefore...
information can be accurately recorded in the recording- and
reproduction area.
According .to an optical information recording
15. method of the.present-invention, information is-recorded
in an area of, the recording. and reproduction area of the
first information recording layer' -through which laser light
passes before,. test recording of the second information
recording layer.. Therefore, accurate recording conditions.
can..be.obtained by the. test. recording.
According. to a. recording and reproduction method of
the present invention, in the-case where an area of the
recording and reproduction area of the first' information.,
recording layer. through which laser light passes is in an
unrecorded state at the time of test recording of the. second
information recording layer,. optimum recording conditions',
are calculated based on the test recording result.
Therefore,, accurate recording conditions can be obtained.'
In a medium according to. the present invention, one.
of the reproduction-only area, and the recording- and
reproduction.4area of the, first information recording layer:
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includes an area through which laser light for recording.
information in the test recording area of the second
information recording. layer passes. The laser, light -for
recording information in the test. recording area of.-the
second information recording layer has passed through the
reproduction-only'areaor-the recording and reproduction
area. Accordingly, the laser light for recording
information in the test recording area of the second
information recording layer. is not influenced bythe
difference between the amount of light passing through the
reproduction-only area of -the' first information recording,,.
layer and the amount of light passing through the recording
and- reproduction area of the-.first information recording
layer. Asa result, accurate recording conditions canbe.
obtained. using the test recording area of the
second
information recording layer.
The -area. of the first information recording layer,
through which the' laser light for recording information in
the 'test recording area.passes, extends ,outward from an.
outer.endof an area of the . first information recording
layer corresponding to the test recording area by a.length. -
6,. the length 6 being represented by:
25- d-tan ('sin"1(NA/n)),
where d is a-distance in a thickness direction between the
first information recording layer and the second
information recording layer; n is a refractive index of the
separation layer; and NA is a. numerical aperture of an
objective lens for.,focusing the laser light to the test
recording area.
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60 - FZ6109
The area of the first information recording layer,
through which the laser light for' recording' information. in
the test recording area passes, extends 'outward-:.fr'om: the,
outer end of the. area of the f ixrst information recording . .
layer corresponding to the test; recording area by a length
8', the length 8' being represented by:
S' d=tan(Bin(NA/A)) + .Sn
where &n is a maximum positional offset distance between-the.-
.,first information recording' layer and the- second
information recording layer..
Accordingly, even when there is-anon-negligible
15'. -offset or.eccentricity in the relative positions of.the
information recording layers,, accurate recording'.-'
conditions for. the second information recording .layer can .
be. obtained' .at the time of test recording of. the second
information recording layer, with no influence of the.
20:- :difference in the amount. of light passing, through the first
information-recording layer.
It- is, preferable to form an area of the second
information recording laser, extending from the and of 'at
'25 least the test recording area by 8 (in the case where there
is a non-negligible offset or eccentricity in the relative
positions of the information recording layers,' by- $'') . into
_-a data recording area. This is preferable in order to expand
the data 'recording- area.
According to the medium of the present invention,
a prescribed area of the first Information recording layer,
which is entirely in a recorded state or an unrecorded state,
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includes an area through which the laser light for recording
information in the test recording area of. the second-
information recording layer passes. The-area of the first
information recording layer., through which the laser light
. 5 for- recording information in the. test recording area of the
secorid information recording.. layer passes,,: is entirely
either in a recorded state or in an-'unrecorded state.
Accordingly, the. laser light for.recording information in
the. test recording area of.. the second 'information recording
10. layer is not influenced by the difference in the amount of.
light caused by the existence of both a recorded state,- area. .
and an unrecorded state area.. As a. result, accurate
recording conditions can be obtained using the. test
recording area of the second- information recording layer.,
The -,prescribed area which is, entirely in an
unrecorded area is, for :`.example;.a recording -prohibited
area.,- a mirror area, or a lead-in area.
20' Regarding a second optical information recording
medium according to the present invention, the area of the.
first information recording layer, through which the laser
light for recording information in the test recording area
of the second information reeordi g layer passes, extends
outward from an outer end of an area of the first information
recording layer corresponding"to the test recording area
by a length b, the-length 8being represented by:
S = d-tan(sin`1(NA/n)).
3.0
where d' is a. distance -in a thickness direction between the
first information recording layer and, the second.
information recording layer; n is a refractive index of the
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separation layer; and NA- is a numerical. aperture of an
objective lens for'focusing the laser light to the test
recording area.
Regarding the second optical information recording
medium according to the present invention, the area of the
first information recording layer, tbrough- which the laser
-light for ,recording information in. the test recording area,
.of. the second information recording layer .passes, extends'
101 outward. from the' outer end .of the. area, of the first,
information recording layer corresponding to' the test
recording area by a,.. length' the length 8' being
represented: by:
8' _. dtan(sin`L(NA/n)) + 8m,
where 8m is a maximum positional offset distance between the
first information recording layer and, the second
information recording layer.
Owing to such, a medium,, even when there. is. a
non-negligible offset or eccentricity in the relative
positions of the information recording layers, accurate .;
recording conditions for the second information recording
layer. can, be .obtained at the time of test recording of the
second information recording. layer, with no influence of
the difference in the amount of light passing through the.
first, information. recording layer:
Regarding the second optical information recording
medium according to the present invention,, it is preferable .
to form an area of the second information recording laser,
extending from the and of at least the test recording area
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by 8 (in, the case where there is a. non-negligible offset or
eccentricity- in -the relative' positions of the, information
recording layers, by '8') into a data recording. area ..: This
.is preferable in order to expand the data-recording-area.
The information for calculating. the - optimum
recording conditions in'- the test recording area are
recorded, in a , specific area of one of a ' plurality . of
recording information layers. Accordingly, even when the
transmittance of ... the area of the first- information
recording layer., through which, the laser light for
recording information in the test recording area of the
second information recording layer passes, is different
from the transmittance of the area of the first, recording
.15 information layer, through which the laser. light, for,
recording information in the. recording and reproduction:
area of the, second. information recording, layer passes,
accurate recording conditions can be calculated for one, of
the layers as long as the recording conditions of the other
layer can be obtained. As a. result, a recording and
reproduction' apparatus -for. starting the optical
information recording medium can immediately learn a method. ,
of calculation which -is - determined from 'the difference
between: the amount of light transmitted through an
25. unrecorded state.area and the amount of light transmitted
through a recorded state area. Accordingly, accurate
recording conditions can be obtained immediately after the,
optical. information recording medium is mounted on 'the
recording and reproduction apparatus.
According to this medium, ' one of the
reproduction-only area and the recording and reproduction.
area of the first information recording layer includes an
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area. through which,laser light for recording information
in' - the recording and. reproduction area of: the second
information recording .layer passes. The' laser light. for..
recording information.-in the recording and' reproduction.
area of the . second information recording layer has passed
..through the reproduction-only- area or the recording and'
reproduction area. - Accordingly, ..the laser light for
recording information in - the recording and reproduction
area of the. second. information :recording layer, is not
influenced by the difference between the, amount of light
passing- through the reproduction-only. area of-,.the 'first
information recording layer and the amount of light passing
through the :' recording. and reproduction area.. of the first
information, recording layer. As a result., accurate
recording conditions can,be obtained using the recording...
and-reproduction area of the second information recording.
layer.
The area of the first information recording layer;.
through which the laser light for recording information in
the recording and reproduction area of the :second
information recording layer passes, extends outward from
an.outer end of an area' of the first information recording
layer corresponding to the recording and reproduction area
25. by a length 8, the; length 8 being represented by:
$ d-tan (sin"1(NA/n)).
where d is a distance in a thickness direction between the .
first information . . recording layer and the . - second
information recording layer; n is a refractive index of the
separation layer, and NA is a numerical aperture. of . -an
objective lens for focusing the - laser' light to the test
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recording area.
The area of the' first information recording layer,
through-which the laser light for recording information in-. .
the recording and reproduction area of the second
information recording layer passes,'extends outward from.
the outer end of the area of the first information recording
layer corresponding to the recording and reproduction area
by a length $'., the length 8' being represented by:'.
d-tan (sin-1(NA/n),) +
where Sm is a -maximum, positional offset-distance between the
first information recording_ layer and the -second
'.information recording layer.
In an ..optical information recording, and
reproduction medium according to the present invention, the
size of the reproduction-only area.of the first information
recording layer can be zero, such that an area influenced
by the reproduction-only area of the first information
recording: layer is minimized at the time of recording An
the recording- and reproduction area of the second
information recording layer. Thus, information can be
recorded accurately on the second information recording
layer.
Owing to this mediuvn, the necessity of forming a
phase -pit in the reproduction-only, area at the time of
..production of the first information, recording layer is
eliminated. Thus, the production process of the disc
substrate can be, simplified.
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The lead-in areas or the, lead-out areas of
corresponding Information recording layers.include a first.
test recording area, a recording and reproduction area, and,
a second test recording area. Therefore,. recording
conditions of different. information recording layers can
be obtained with only the lead-in areas or the lead-out'
areas. In this case, the non-uniform light- prevention area
of:the-first information recording layer includes an,area
:.of.-. the first information recording, layer through : which-
laser light for recording information in the test, recording
. area of the second.-information recording layer passes..
The. non-uniform light. prevention area is 'for
example, a reproduction-only area.
The. non-uniform light prevention area is, :for
example, an area formed of at least one of the, group
consisting of a reproduction-only area, a recording"
prohibited area, and;a mirror area.
The area of the first. information recording layer,
through which the. laser light for recording information in
the test recording area of the second information recording
layer passes, extends outward from an outer end of an area
of the first, information recording layer corresponding to.
the test recording area. by a length 8, the length:8 being
represented. by:
8 dtan(si.n''(NA/n).),
where d is a distance in it. thickness direction between the
first' information 'recording layer and the.. second,
information recording layer; n is a refractive index of the
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separation layer; and NA is a numerical aperture of an.
objective lens for focusing. the laser light to..the test
recording area.
The area of the. first information recording layer,
through which.the laser light for recording information in
the test recording area, of the. second..nformation recording
layer passes, extends outward from the outer and of the area
of the- first information recording layer corresponding to.
the test recording area by a length S' the length S' being
represented by:
d=tan (sin"1(NA/n ).) + Sm
where. 8m is a maximum positional offset distance between the
first information recording. layer, and the second
information recording layer.
Accordingly, even when there is a nor-negligible
.20 offset or eccentricity in. the' relative positions of the
information recording layers, accurate recording
conditions for the second information recording layer can'.
be.obtained at' the time of test recording of the second
information recording layer, with no influence of the
difference in the amount of, light passing through, the first
information recording layer
According to the method of the present invention,
before. information is recorded in the test recording area
of the second. information recording layer, information is
stored in an area of the first information recording layer
through which laser light for recording information in the
test recording area of the second information recording
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layer passes. Accordingly, the laser light for recording
information in the 'test recording area of. the second
Information- recording layer is... not 'influenced by- the
difference in the amount of. light which is caused by. the
5- first information recording. layer having both a:recorded
state area and an unrecorded state area. As a result,
accurate- recording conditions can be obtained by test.
recording of the second information recording layer-:.
The area of the first information recording layer,
through which.the laser light for recording .information in
the test recording. area of the second information recording.
layer passes, extends outward .from an outer end of .'an area
of the first information recording layer corresponding to
the test recording area by a length 6,.-the length $'being
represented by.
S - d=tan(ain"1(NA/n) ).
where d is a distance in' .a thickness direction between. the...
first information recording layer and the ..second
information recording layer; n is a refractive.index.,of the, .
separation layer; and NA is a numerical aperture 'of an
objective lens for focusing the laser light to-the test.
.25. recording area
The area of the first information recording layer,
'through which the laser light for recording information in
the test recording area of the second information recording
.30 layer passes, extends outward from the outer end of the area
of the first, information recording layer corresponding to.-
the test ' recording area-by a length V, the length 8' being
represented by:
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$' = d=tan (sin-.1(NA/n) ): + &R.
where am is a maximum'positional offset distance between the
first information recording layer and the -second
information recording layer.
Owing to such' a method', even when there is a
non-negligible, offset or eccentricity in the relative
.10. positions of the information recording. layers,7 accurate
recording conditions can:be obtained at the'time of test.
recording of the second information recording layer, with
no influence of the difference in the amount of light; caused
by the. first information recording layer' having both a
recorded state area and an unrecorded state-'area.
The information which is recorded in:advance may be;
for example, information obtained by modulating dummy
information..
The information.may be recorded in advance by a
certification step..
According to the method of the present invention,
optimum recording conditions for the second information
recording layer can be-calculated based on the function
and/or the state of the area of the first. information
recording layer through which the laser light for recording
information in the' test -recording area of -the second
.30 information recording layer passes.
The area of, the first information recording layer',
through which the laser light for recording information in
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..the -test recording area of the second information recording.
layer passes, extends: outward from an 'outer*' end of an area
of the first information recording 'layer corresponding.:to
the test recording area by- a length 8,. the length S being
.5 represented by:
S =. d=tan(sin'1(NA/n) ).:
where d Is a distance in a thickness direction between the
first information recording layer 'and-. the second
Information recording layer; n is a refractive index of the
separation layers-, and NA is ' a numerical :aperture of, an
objective lens for focusing the laser light :to the test
recording area.
.
The area of-'the first information recording layer,
through which the. laser. light f or recording 'information in
the test recording area of the second information recording
layer passes, extends outward from. the outer, end of the area
of the first information recording layer corresponding to the test recording
area .by a length 8' the ,length- 8' being
represented by:
8' s d=tan(sin_y (Nk/n)) + Stn .
where &n is a maximum positional off set distance: between. the
first information recording layer and. the second.
information recording layer.
Owing, to this method, even when there is, a.
non-negligible offset' or eccentricity in. the relative
positions of the information 'recording layers, accurate.
recording conditions can be obtained at = the. time of test
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recording of the second information recording layer, based
on the difference between the amount' of. light transmitted
through ;an unrecorded state area of, the first information:
recording layer and the amount of light transmitted through.
a recorded state area of . the first information recording
layer.
It is preferable' to- record information for
-calculating the optimum recording conditions in a specific.
area of-the optical information recording medium.' '
Thus, even when. the method of calculation is
different medium by medium, the. recording. and, reproduction
apparatus can immediately learn the.method of calculation.:,.:
Therefore, the time. required for actually recording
information after the medium is mounted on,the apparatus.
can be shortened: .. .
According to the-optical information recording.'
apparatus of the present invention, even when an-area of
the, first information recording layer, through which laser
light for recording information in the test, recording area of the
second.information recording layer passes, includes
an unrecorded'state area, the laser light for recording
information in' the test recording area of the second
information, recording layer records the information in the.
area of the first information recording layer, before
recording the information 'in the test recording area of the"
second. information recording layer. Therefore', there is.
no influence of the difference in the ' amount of light,
caused by the laser light for recording information in the,
test recording area of the second information recording
layer passing through an area including both a recorded
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state area and an unrecorded state area. As a result,
accurate recording conditions for the ' sedond information
recording layer can be obtained.
